WIP try and fail to report this more precisely

Author: Blaisorblade

compiler/src/dotty/tools/dotc/core/TypeErrors.scala

@@ -112,8 +112,10 @@ class CyclicReference private (val denot: SymDenotation, var inImplicitSearch: B
         cx.tree match {
           case tree: untpd.ValOrDefDef if inImplicitSearch && !tree.tpt.typeOpt.exists =>
             // Can happen in implicit defs (#4709) or outside (#3253).
-            TermMemberNeedsNeedsResultTypeForImplicitSearch(cycleSym)
+            TermMemberNeedsNeedsResultTypeForImplicitSearch(tree.name)
           case tree: untpd.DefDef if !tree.tpt.typeOpt.exists =>
+            // The reported symbol is more correct, but it might *not* be a method!
+            // OverloadedOrRecursiveMethodNeedsResultType(cycleSym.name)
             OverloadedOrRecursiveMethodNeedsResultType(tree.name)
           case tree: untpd.ValDef if !tree.tpt.typeOpt.exists =>
             RecursiveValueNeedsResultType(tree.name)

compiler/src/dotty/tools/dotc/reporting/diagnostic/messages.scala

@@ -2111,13 +2111,13 @@ object messages {
   }
 
   // Relative of CyclicReferenceInvolvingImplicit and RecursiveValueNeedsResultType
-  case class TermMemberNeedsNeedsResultTypeForImplicitSearch(cycleSym: Symbol)(implicit ctx: Context)
+  case class TermMemberNeedsNeedsResultTypeForImplicitSearch(cycleSymName: Names.TermName)(implicit ctx: Context)
     extends Message(TermMemberNeedsNeedsResultTypeForImplicitSearchID) {
     val kind = "Syntax"
-    val msg = hl"""$cycleSym needs result type because its right-hand side attempts implicit search"""
+    val msg = hl"""Member $cycleSymName needs result type because its right-hand side attempts implicit search"""
     val explanation =
-      hl"""|The right hand-side of $cycleSym's definition requires an implicit search at the highlighted position.
-           |To avoid this error, give `${cycleSym.name}` an explicit type.
+      hl"""|The right hand-side of $cycleSymName's definition requires an implicit search at the highlighted position.
+           |To avoid this error, give `${cycleSymName}` an explicit type.
            |""".stripMargin
   }
 }